The present invention generally discloses a safety system for a high pressure gas well and more particularly involves a shutdown system which is "normally open" rather than one that is "normally closed".
Prior art systems currently in use on such wells usually comprise only a pop-off safety valve installed in the flowline from the wellhead. When a pressure surge or build-up occurs in the well and is transmitted to the wellhead, before the pressure can rupture the weaker flowline, it is bled to the atmosphere through the pop-off valve. This protects the flowline from rupturing under high wellhead pressures, but suffers the disadvantage of providing a free vent to atmosphere of explosive and/or toxic gas. Usually this will continue to vent to atmosphere until the well operator returns to the well site and notices the well condition or until the pressure surge dies out.
Other safety systems utilized on gas wells are of the type known as "normally closed" systems. These systems use some parameter of the well operation to maintain a flow valve open against a biasing force continuously urging the flow valve to a closed, non-flow position. If any malfunction occurs in the safety system unrelated to a high pressure surge from the well, the flow valve will close off production from the well even though there is no danger of high pressure blowout in the flowline. Production from the well will be lost to the well owner until the operator notices the shutdown condition and cures the malfunction in the safety system.
The present invention overcomes these disadvantages by providing a safety shutdown system that does not vent free-flowing production gas into the atmosphere nor does it close off production in response to a malfunction occurring in the safety system.
This is accomplished by inserting a motor valve between the wellhead and the flowline, a pressure sensor in the flowline, and an operating pressure line downstream of the sensor, passing through the sensor, and communicating well pressure to operate the motor valve.